1. Field of the Invention
This invention relates to a load interrupter device especially useful for live front padmounted high voltage switchgear having manually operable switch structure which includes either a fuse or a disconnect switchblade.
2. Description of the Prior Art
Padmounted electrical switchgear for use in electrical distribution systems and particularly underground systems, may be of the air-insulated, live front type in order to provide desirable in-air visibility, in-air switching and in-air installation. Switchgear of this type often includes fuses to protect the distribution system from fault currents while providing coordination with upstream and downstream protective devices.
The switchgear has manually actuated switch structure which allows a lineman to selectively open distribution circuits connected to the switchgear. The switch structure may include a swingable switchblade, or if a power fuse is provided, the fuse may serve as the pivotal switch element. In either event, it is necessary that a load interrupter be provided in association with the switch in order to prevent arcing from occurring across the switch elements during opening of the switch by the lineman.
Load interrupters have previously been provided for this purpose, as for example the device which is shown and described in U.S. Pat. No. 4,268,811. In that device, a moveable conductive element mounted within an insulative housing is connected to a shiftable terminal forming a part of the switch. The conductive element normally engages internal contacts within the body of the device that are in turn electrically connected to a second fixed terminal. An extension on a pivotally mounted power fuse releasably engages the moveable terminal so that when the power fuse is pivoted to open the circuit, the moveable terminal and thereby the conductive element in the interrupter body are shifted to disconnect the element from its associated contacts. Synthetic resin material within the interrupter body produces gases when an arc is drawn between the conductive element and the internal contacts to extinguish an arc that is drawn between the contacts and the elements upon separation of the conductive components.
In the interrupter device of the '811 patent, the time required to effect separation of the conductive element from its associated contacts, is a function of the speed with which the lineman pulls on the fuse to disengage the extension thereof from the interrupter device contacts. If that speed of manual operation is relatively slow, undesirable major arcing can occur within the interrupter body.
Also, since the arc is drawn between the contacts that carry the continuous current load, damage that might occur during excessive arcing could effect the ability of the device to carry the continuous load current without overheating, and eventually burning up of the components.